Electrode catheters have been in common use in medical practice for many years. They are used to stimulate and map electrical activity in the heart and to ablate sites of aberrant electrical activity.
In use, the electrode catheter is inserted into a major vein or artery, e.g. a femoral artery, and then guided into the chamber of the heart which is of concern. Within the heart, the ability to control the exact position and orientation of the catheter tip is critical, and largely determines the success of the catheter treatment.
Steerable (or deflectable) catheters are well-known. For example, a catheter having a control handle comprising a housing having a piston chamber at its distal end is described in U.S. Pat. No. RE 34,502, the entire content of which is incorporated herein by reference. In that control handle, a piston is mounted in the piston chamber and is afforded lengthwise movement. The proximal end of the catheter body is attached to the piston. A puller wire is attached to the housing and extends through the piston and through the catheter body. The distal end of the puller wire is anchored in the tip section of the catheter. In this arrangement, lengthwise movement of the piston relative to the housing results in deflection of the catheter tip section.
However, this design is generally limited to catheters having a single puller wire. Bi-directional catheters, i.e. catheters capable of deflecting in more than one direction without rotating the catheter body, require more than one puller wire. When two puller wires are used, it is undesirable for both wires to be moved simultaneously in the same direction. Therefore, the piston control handle design for single puller wire catheters is not well-suited for a two puller wire system, and a need exists for a control handle for a bi-directional catheter capable of independently moving the two puller wires and preventing simultaneous movement of the puller wires in the same direction.